Magnetic responsive amphiphilic janus nanoparticles, preparation method thereof and application thereof in surfactants and droplet microfluidics

Abstract

The application belongs to the technical field of materials, and particularly relates to a magnetic response amphiphilic Janus nanoparticle, a preparation method thereof, and application thereof in surfactants and droplet microfluidics. The preparation method of the magnetic response amphiphilic Janus nanoparticle can adjust the size, morphology and amphiphilic proportion of the magnetic response amphiphilic Janus nanoparticle, and further accurately control the structure of the Janus nanoparticle. Moreover, the prepared magnetic response amphiphilic Janus nanoparticle simultaneously has three components, can be used as a solid surfactant to stabilize a Pickering emulsion, has good emulsion stability, and has obvious magnetic response. The magnetic response amphiphilic Janus nanoparticle can directly generate a large number of emulsion droplets with good stability, uniform size and adjustable magnetic response through microfluidic technology.

Description

Technical Field

[0001] This invention belongs to the field of materials technology, specifically relating to magnetically responsive amphiphilic Janus nanoparticles and their preparation methods, as well as their applications in surfactants and droplet microfluidics. Background Technology

[0002] Oil-water biphase reactions are of great significance in organic synthesis, petroleum processing, and enzymatic reactions. However, the efficiency of oil-water reactions is limited by the low interfacial area resulting from the immiscibility of water and oil. Therefore, forming a stable emulsion to maximize the interaction area is essential for improving its practicality. To form a stable emulsion, amphiphilic organic surfactants or solid nanoparticles are generally used to stabilize the oil-water interface.

[0003] Currently, common methods for emulsion generation include mechanical stirring, high-pressure homogenization, and ultrasonic emulsification. However, emulsions generated by these methods suffer from drawbacks such as uneven size distribution. Droplet microfluidics is a novel emulsion generation technology that features uniform droplet size, diverse structures, and good monodispersity. Furthermore, droplet size can be precisely adjusted by combining various microchannels with different geometries and controlling the two-phase flow rates to obtain emulsion droplets of customized sizes. However, the surfactants used in preparing emulsion droplets using droplet microfluidics are mostly molecular amphiphilic organic surfactants, with particulate surfactants being rarely used. This is mainly because ordinary particles tend to aggregate and clog channels. Therefore, designing nanoparticle surfactants with special structures is crucial.

[0004] Similar to traditional organic surfactants with hydrophilic / hydrophobic ends, Janus nanoparticles are more advantageous for stabilizing Pickering emulsions because the two sides of the Janus particle can be located in their respective affinity phases (oil or water) to reduce thermodynamic energy. The emulsion stabilizing ability of molecular amphiphilic surfactants varies with the hydrophobic carbon chain and hydrophilic ionic head. The hydrophilic / hydrophobic ratio of traditional organic amphiphilic surfactants can be adjusted by changing the carbon chain length. Correspondingly, the emulsifying ability of Janus particles also largely depends on the volume ratio of their hydrophilic / hydrophobic regions at different ends. However, precisely adjusting the hydrophilic / hydrophobic ratio of asymmetric Janus nanoparticles is quite difficult. Furthermore, Janus particles can also possess various properties such as magnetic responsiveness, infrared responsiveness, and temperature responsiveness, and the resulting Pickering emulsions also exhibit responsive characteristics. However, the obtained Janus particles are mostly limited to two different components, and the responsiveness is mostly obtained by adjusting pH or temperature.

[0005] To date, various methods have been developed for preparing Janus particles, including droplet microfluidics, planar template methods, and polymer molecular assembly methods. Droplet microfluidics, in particular, uses droplets containing different substances, obtained beforehand using a microfluidic chip, to create micro / nano structures through photopolymerization or thermopolymerization. However, the fabrication process for microfluidic chips is complex, and selecting the appropriate three-phase fluid material for forming droplets containing different substances is challenging. Furthermore, controlling droplet formation requires a high level of expertise, and the resulting Janus particles are mostly micrometer-sized, with nanoparticles proving difficult to obtain. These limitations restrict its mass production and practical applications.

[0006] The planar template method functionalizes the exposed portions of monolayer distributed particles while leaving the particles close to the plane intact. However, functionalizing monolayer particles requires expensive equipment, and the resulting Janus particles are mostly spherical. The polymer molecular assembly method involves dissolving different block polymers in a mixed solvent, then transferring them to a less suitable solvent. During solvent evaporation, the block copolymers precipitate asymmetrically due to their different solubilities, forming Janus particles. However, the limited selectivity of the block copolymers and co-solvents used as raw materials makes it difficult to control the morphology and size of Janus particles during preparation. Summary of the Invention

[0007] To overcome the shortcomings of the prior art, the first objective of this invention is to provide a method for preparing magnetically responsive amphiphilic Janus nanoparticles. This method is simple, has low production costs, and allows for easy adjustment of the size, morphology, and amphiphilic ratio of the Janus nanoparticles. It can precisely control the structure of the Janus nanoparticles and enable them to contain multiple components and possess multiple functions.

[0008] A second objective of this invention is to provide magnetically responsive amphiphilic Janus nanoparticles that can be directly used as solid surfactants in droplet microfluidics to generate stable, uniformly tunable, magnetically responsive emulsion droplets.

[0009] A third objective of this invention is to provide the application of magnetically responsive amphiphilic Janus nanoparticles in solid surfactants.

[0010] A fourth objective of this invention is to provide a method for preparing a Pickering emulsion using the aforementioned magnetically responsive amphiphilic Janus nanoparticles.

[0011] The fifth objective of this invention is to provide the application of magnetically responsive amphiphilic Janus nanoparticles in droplet microfluidics.

[0012] One of the objectives of this invention can be achieved by adopting the following technical solutions:

[0013] A method for preparing magnetically responsive amphiphilic Janus nanoparticles is provided. This method involves polymerizing magnetic nanoparticles with monomers and a crosslinking agent to obtain hydrophobic seed particles. Then, a hydrophilic polymer monomer is coated onto one end of the seed particles using a seed swelling method, ultimately yielding magnetically responsive amphiphilic Janus nanoparticles. The method includes the following steps:

[0014] Preparation of seed particles: Magnetic nanoparticles, monomers and crosslinking agents are dispersed in an organic solvent, and then the resulting mixture is added to a polar solvent. After stirring under an inert gas atmosphere, an initiator is added, and stirring is continued under an inert gas atmosphere. The reaction is carried out while stirring and heating. Then, the mixture is centrifuged and washed to obtain seed particles.

[0015] Preparation of magnetically responsive Janus particles: The seed particles were dispersed in a mixture containing a nonpolar solvent and an alkaline solution, and then a hydrophilic polymer monomer was added. The mixture was stirred and reacted at room temperature, followed by centrifugation and washing to obtain magnetically responsive Janus particles.

[0016] The method for preparing magnetically responsive amphiphilic Janus nanoparticles of the present invention yields magnetically responsive amphiphilic Janus nanoparticles with a particle size of 100 nm-500 nm, containing three components, thus exhibiting better application value. Furthermore, by adjusting the amounts of monomers and hydrophilic polymer monomers, the size, morphology, and amphiphilic ratio of the magnetically responsive amphiphilic Janus nanoparticles can be adjusted, thereby enabling precise control of the Janus nanoparticle structure and demonstrating good stability.

[0017] Furthermore, in the preparation of the seed particles, the magnetic nanoparticles include iron(III) oxide and / or barium ferrite; wherein, barium ferrite can be purchased directly from commercial sources. Additionally, both iron(III) oxide and barium ferrite possess excellent magnetic properties.

[0018] Furthermore, the preparation of the iron oxide is as follows: ferrous chloride tetrahydrate and ferric chloride hexahydrate are dissolved in hydrochloric acid, and ammonia is added. Nanoparticles are obtained through a co-precipitation reaction. After adding a hydrophobic reagent, the mixture is stirred for 1-5 hours to modify the nanoparticles for hydrophobicity. After washing, magnetic iron oxide nanoparticles are obtained and dispersed in octane, toluene or cyclohexane for storage.

[0019] Furthermore, the hydrophobic agent includes at least one of oleic acid, methacryloxypropyltrimethoxysilane, and dimethyloctadecyl[3-trihydroxysilylpropyl]ammonium chloride;

[0020] The molar ratio of ferrous chloride tetrahydrate to ferric chloride hexahydrate is 1:1-5; this molar ratio can prepare iron(III) oxide with suitable particle size.

[0021] The iron(III) oxide is in the γ-crystalline form with a particle size of 8 nm-12 nm. This crystalline form and particle size of iron(III) oxide exhibits excellent reactivity.

[0022] Furthermore, in the preparation of the seed particles, the monomer includes styrene or methyl methacrylate; wherein styrene or methyl methacrylate, as monomers, has excellent reactivity.

[0023] Furthermore, the mass ratio of the magnetic nanoparticles to the monomer is 1:2-6; this mass ratio enables the prepared magnetically responsive amphiphilic Janus nanoparticles to have a nanometer-scale particle size, and their morphology and size are suitable for direct use in droplet microfluidics.

[0024] Furthermore, the crosslinking agent includes dicumyl peroxide or divinylbenzene; dicumyl peroxide or divinylbenzene has good crosslinking properties.

[0025] Furthermore, the amount of the crosslinking agent is 0.5%-3% of the monomer mass;

[0026] Furthermore, the organic solvent includes at least one of octane, toluene, or cyclohexane;

[0027] Furthermore, the polar solvent is an aqueous solution containing a nonionic surfactant, wherein the concentration of the nonionic surfactant in the aqueous solution is 1.2 g / L-3.0 g / L, and the nonionic surfactant includes at least one of Tween 20, Span 80, or Triton X-405.

[0028] Furthermore, the amount of the polar solvent used is 50-100 times the mass of the monomer; this amount of polar solvent can provide a better reaction environment.

[0029] Furthermore, the inert gas includes nitrogen or argon; wherein, nitrogen or argon, as an inert gas, has a better protective effect.

[0030] Furthermore, the initiator includes an aqueous solution of azobisisobutyronitrile or an aqueous solution of potassium persulfate; this initiator can effectively promote the polymerization reaction.

[0031] Furthermore, the amount of initiator used is 1%-5% of the monomer mass; this amount of initiator is sufficient to effectively promote the polymerization reaction.

[0032] Furthermore, the dispersion method includes one of ultrasound, vortexing, or stirring; wherein ultrasound, vortexing, or stirring are all easy-to-operate methods with relatively low operating costs.

[0033] Furthermore, the resulting mixture is dispersed in a polar solvent and stirred under an inert gas atmosphere for 0.5-1 hour. An initiator is then added, and stirring continues under an inert gas atmosphere for 1-3 hours. While stirring, the mixture is heated to 60-80°C and reacted for 18-24 hours. The mixture is then centrifuged and washed three times alternately with water and anhydrous ethanol to obtain seed particles, which are then dispersed in ethanol for storage. The stirring speed is 300-900 rpm. The above polymerization reaction conditions are relatively mild, and the operating cost is low, making it suitable for large-scale production applications.

[0034] Furthermore, in the preparation of the magnetically responsive Janus particles, the mass ratio of the seed particles to the mixture is 1:500-700; in the mixture, the mass ratio of the nonpolar solvent to the alkaline solution is 1:1.5-2.5; the nonpolar solvent includes at least one of ethanol or isopropanol.

[0035] Furthermore, the alkaline solution includes at least one of ammonia, triethanolamine, or aminomethylpropanol.

[0036] Furthermore, the hydrophilic polymer monomer includes at least one of lactic acid, acrylic acid, or ethyl orthosilicate; wherein, lactic acid, acrylic acid, or ethyl orthosilicate, as hydrophilic polymer monomers, not only have the advantage of good hydrophilicity, but also good reactivity and low production cost.

[0037] Furthermore, the mass ratio of the seed particles to the hydrophilic polymer monomer is 1:13-56; this mass ratio of seed particles to hydrophilic polymer monomer results in magnetically responsive amphiphilic Janus nanoparticles with nanoscale particle size, adjustable hydrophilic and oleophilic properties, and morphology and size suitable for direct use in droplet microfluidics.

[0038] Furthermore, the stirring reaction time is 6-20 hours, and the stirring speed is 200-500 rpm. The stirring operation promotes the reaction and results in more uniform particle size of the prepared magnetically responsive amphiphilic Janus nanoparticles.

[0039] Furthermore, the washing process involves alternating between water and anhydrous ethanol three times. This alternating washing with water and anhydrous ethanol three times ensures thorough cleaning.

[0040] The second objective of this invention can be achieved by adopting the following technical solution:

[0041] A magnetically responsive amphiphilic Janus nanoparticle is provided, prepared by the method described above. This magnetically responsive amphiphilic Janus nanoparticle has a particle size of 100nm-500nm, exhibits uniform size, and contains three components, thus possessing greater application value. Furthermore, this Janus nanoparticle can be directly used in droplet microfluidic generation to produce stable, uniformly sized, and magnetically responsive emulsion droplets.

[0042] The third objective of this invention can be achieved by adopting the following technical solutions:

[0043] This study provides information on the application of magnetically responsive amphiphilic Janus nanoparticles in surfactants.

[0044] The magnetically responsive amphiphilic Janus nanoparticles prepared in this invention are used as solid surfactants.

[0045] The fourth objective of this invention can be achieved by adopting the following technical solutions:

[0046] A method for preparing a Pickering emulsion is provided, the Pickering emulsion comprising magnetically responsive amphiphilic Janus nanoparticles obtained by the method described above, comprising the following steps:

[0047] The magnetically responsive amphiphilic Janus nanoparticles are dispersed in an aqueous phase, and then an oil phase is added. The oil and water phases are emulsified by stirring to form a water-in-oil or oil-in-water Pickering emulsion, thus obtaining the Pickering emulsion.

[0048] This invention discloses a method for preparing a Pickering emulsion, which has the advantages of being mild and low-cost. The resulting Pickering emulsion exhibits tunable amphiphilicity and can be directly generated into stable, uniformly sized, and magnetically corresponding emulsion droplets using microfluidic technology.

[0049] Furthermore, the dispersion method includes ultrasound; ultrasound can uniformly disperse magnetically responsive amphiphilic Janus nanoparticles in an aqueous phase, and the operating cost is relatively low.

[0050] Furthermore, the oil phase includes at least one of hexadecane, mineral oil, or soybean oil; wherein the selected oil phase is suitable for forming emulsion droplets and is relatively inexpensive.

[0051] Furthermore, the stirring method includes vortex; wherein, stirring by vortex can make the oil and water phases emulsify evenly and has a relatively low operating cost.

[0052] Furthermore, the stirring speed is 200 rpm to 500 rpm, and the stirring time is 6 h to 20 h.

[0053] Furthermore, in the Pickering emulsion, the concentration of the magnetically responsive amphiphilic Janus nanoparticles is 0.4 mg / mL to 2 mg / mL; this concentration of Pickering emulsion is suitable for use as a surfactant.

[0054] Furthermore, the volume ratio of the aqueous phase to the oil phase is 1-9:1-9; this volume ratio makes the prepared surfactant suitable for direct use in droplet microfluidics.

[0055] Furthermore, when the mass ratio of the seed particles to the hydrophilic polymer monomer is <1:38, the Pickering emulsion formed using the magnetically agitated amphiphilic Janus nanoparticles is an oil-in-water emulsion; when the mass ratio of the seed particles to the hydrophilic polymer monomer is >1:38, the Pickering emulsion formed using the magnetically agitated amphiphilic Janus nanoparticles is a water-in-oil emulsion. By adjusting the mass ratio of the seed particles to the hydrophilic polymer monomer, the synthesized particles can have different hydrophilicity / hydrophobicity, thus resulting in different types of Pickering emulsions.

[0056] The Pickering emulsion prepared by this invention has adjustable amphiphilicity and can directly generate stable, uniformly sized, and magnetically corresponding emulsion droplets through microfluidic technology.

[0057] The fifth objective of this invention can be achieved by adopting the following technical solutions:

[0058] Application of magnetically responsive amphiphilic Janus nanoparticles prepared by a specific method in droplet microfluidics.

[0059] Furthermore, the magnetically responsive amphiphilic Janus nanoparticles are used in microfluidic channels and dispersed in a dispersed phase as the inner phase, with a fluid of opposite polarity to the inner phase as the outer phase. The inner and outer phases are introduced into a flow-focusing PDMS microfluidic chip or a glass capillary device by a fluid injection pump or a pressure injection pump. By adjusting the flow rate and flow rate ratio of the two phases, the size of the generated droplets is controlled to obtain water-in-oil droplets or oil-in-water droplets.

[0060] Furthermore, when forming oil-in-water droplets, the volumetric flow rate ratio of the internal phase to the external phase is 1:20-280; when forming water-in-oil droplets, the volumetric flow rate ratio of the internal phase to the external phase is 1:1-15.

[0061] Specifically, when the Pickering emulsion is formed by droplet microfluidics, the size dispersion of the resulting Pickering emulsion is <5%. Furthermore, the Pickering emulsion exhibits a response range of 0.1T–0.7T to an applied magnetic field.

[0062] Among them, the magnetically responsive amphiphilic Janus nanoparticles of the present invention can directly generate a large number of stable, uniformly tunable emulsion droplets with magnetic response through microfluidic technology.

[0063] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0064] (1) The method for preparing magnetically responsive amphiphilic Janus nanoparticles of the present invention involves polymerizing magnetic nanoparticles with monomers and crosslinking agents to obtain hydrophobic seed particles, and then polymerizing and coating one end of the seed particles with hydrophilic polymer monomers using a seed swelling method to finally obtain magnetically responsive amphiphilic Janus nanoparticles. The obtained magnetically responsive amphiphilic Janus nanoparticles have a particle size of 100nm-500nm, which has better application value. Furthermore, by changing the ratio of seed particles to hydrophilic polymer monomers, the size, morphology, and amphiphilicity of the magnetically responsive amphiphilic Janus nanoparticles can be adjusted, achieving precise control of the Janus nanoparticle structure. This preparation method has the advantages of mild conditions and low cost.

[0065] (2) The magnetically responsive amphiphilic Janus nanoparticles of the present invention are nanoscale in size and simultaneously possess three components, thus having a wider range of applications. They have significant application value in the fields of solid emulsifiers and droplet microfluidics, and can be directly used in droplet microfluidics to generate stable, uniformly sized, and magnetically responsive emulsion droplets. Furthermore, these magnetically responsive amphiphilic Janus nanoparticles have the advantage of precisely controlled hydrophilic-hydrophobic structures, i.e., the ratio of hydrophilic to hydrophobic parts can be adjusted. These particles can be used to form various types of Pickering emulsions, which exhibit good emulsion stability and significant magnetic response.

[0066] (4) The magnetically responsive Janus nanoparticles of the present invention can be used as solid surfactants to prepare stable Pickering emulsions. The emulsions exhibit good stability and can remain stable for a long time, with a stability period of more than one month. In addition, the magnetically responsive Pickering emulsion has good application prospects in fields such as drug release and crude oil recovery. Furthermore, the magnetic response is convenient, non-toxic, and can induce a response in the emulsion without affecting its own properties.

[0067] (5) Application of the magnetically responsive amphiphilic Janus nanoparticles of the present invention in droplet microfluidics. The magnetically responsive amphiphilic Janus nanoparticles can directly generate a large number of stable, uniformly sized, and magnetically responsive emulsion droplets through microfluidic technology. Attached Figure Description

[0068] Figure 1 This is a scanning electron microscope image of the magnetically responsive amphiphilic Janus nanoparticles obtained in Example 1 of the present invention.

[0069] Figure 2 The figures show the infrared absorption spectra of the magnetic nanoparticles, seed particles, and magnetically responsive amphiphilic Janus nanoparticles obtained in Example 1 of this invention. In the figures, Fe3O4 NPs represent magnetic nanoparticles, Fe3O4@PS NPs represent seed particles, and Fe3O4@PS-SiO2 NPs represent magnetically responsive amphiphilic Janus nanoparticles.

[0070] Figure 3 The image shows the hysteresis loop and response diagram of the magnetically responsive amphiphilic Janus nanoparticles prepared in Example 1 of this invention under a magnetic field.

[0071] Figure 4 This refers to the water-in-oil emulsions formed by mechanical emulsification of magnetically responsive amphiphilic Janus nanoparticles at four different oil-to-water ratios in Example 3 of this invention. In the figure, the oil-to-water ratio of the emulsion labeled a is 1:9, the oil-to-water ratio of the emulsion labeled b is 3:7, the oil-to-water ratio of the emulsion labeled c is 5:5, and the oil-to-water ratio of the emulsion labeled d is 7:3.

[0072] Figure 5 This is a fluorescence image of the water-in-oil emulsion formed by mechanical emulsification of magnetically responsive amphiphilic Janus nanoparticles in Example 3 of the present invention at an oil-water ratio of 1:9.

[0073] Figure 6 This refers to the oil-in-water emulsions formed by mechanical emulsification of magnetically responsive amphiphilic Janus nanoparticles at four different oil-to-water ratios in Example 4 of this invention. In the figure, the oil-to-water ratio of the oil-in-water emulsion labeled a is 1:9, the oil-to-water ratio of the oil-in-water emulsion labeled b is 3:7, the oil-to-water ratio of the oil-in-water emulsion labeled c is 5:5, and the oil-to-water ratio of the oil-in-water emulsion labeled d is 7:3.

[0074] Figure 7 This is a fluorescence image of the oil-in-water emulsion formed by mechanical emulsification of magnetically responsive amphiphilic Janus nanoparticles in Example 4 of the present invention at an oil-water ratio of 1:9.

[0075] Figure 8The images show physical images of the water-in-oil emulsion and optical microscope images of the droplets obtained from the application of magnetically responsive amphiphilic Janus nanoparticles in droplet microfluidics in Example 5 of this invention. The upper image is the physical image of the generated water-in-oil emulsion, and the lower image is the optical microscope image of the droplets.

[0076] Figure 9 The images show physical images of the oil-in-water emulsion obtained from the application of magnetically responsive amphiphilic Janus nanoparticles in droplet microfluidics in Example 6 of this invention, along with optical microscope images of the droplets. The upper image shows the physical image of the generated oil-in-water emulsion, and the lower image is an optical microscope image of the droplets. Detailed Implementation

[0077] To make the technical problem to be solved, the technical solution, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0078] The terminology used in the embodiments of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. In this invention, the singular forms “a,” “the,” and “the” as used in the embodiments and appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0079] The technical solution of the present invention will now be clearly and completely described with reference to specific embodiments. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0080] To help better understand this invention, the following concepts are explained:

[0081] Janus particles are particles with asymmetrical structures that have different chemical compositions and morphologies. This structure allows Janus particles to exhibit amphiphilic properties, similar to traditional molecular surfactants, and can be used to form stable Pickering emulsions.

[0082] Pickering emulsions are emulsions stabilized using solid particulate surfactants. After emulsion formation, the solid particles are adsorbed at the interface between the two phases and reach a stable state. These emulsions are characterized by good stability, low toxicity, and readily available responsiveness.

[0083] Droplet microfluidics is a novel method for preparing droplets that uses two immiscible liquids as the dispersed and continuous phases, utilizing fluid shear forces to shear the dispersed phase into droplets. This droplet generation method offers advantages such as good uniformity, continuous controllability, and adjustable size.

[0084] Amphiphilicity refers to the property of being both hydrophilic and lipophilic.

[0085] A method for preparing magnetically responsive amphiphilic Janus nanoparticles includes the following steps:

[0086] Preparation of seed particles: Magnetic nanoparticles, monomers, and crosslinking agents are dispersed in an organic solvent. The resulting mixture is then added to a polar solvent and stirred under an inert gas atmosphere. An initiator is then added, and stirring continues under an inert gas atmosphere while heating the mixture. The mixture is then centrifuged and washed to obtain seed particles. The obtained seed particles are dispersed in an organic solvent and stored for later use. Ethanol can be used as the organic solvent.

[0087] Preparation of magnetically responsive Janus particles: Seed particles were dispersed in a mixture containing a nonpolar solvent and an alkaline solution, then a hydrophilic polymer monomer was added, and the mixture was stirred and reacted at room temperature. After centrifugation and washing, magnetically responsive Janus particles were obtained.

[0088] The method for preparing this magnetically responsive amphiphilic Janus nanoparticle involves polymerizing magnetic nanoparticles with monomers and crosslinking agents to obtain hydrophobic seed particles. Then, a hydrophilic polymer monomer is coated onto one end of the seed particles using a seed swelling method, ultimately yielding the magnetically responsive amphiphilic Janus nanoparticles. The obtained magnetically responsive amphiphilic Janus nanoparticles have a particle size of 100nm-500nm and contain three components, offering greater application value. Furthermore, by adjusting the amounts of monomers and hydrophilic polymer monomers, the size, morphology, and amphiphilic ratio of the magnetically responsive amphiphilic Janus nanoparticles can be adjusted, thereby enabling precise control of the Janus nanoparticle structure and exhibiting good stability.

[0089] In some embodiments, during the preparation of the seed particles, the magnetic nanoparticles comprise magnetite (Fe3O4) and / or barium ferrite; wherein, barium ferrite can be purchased directly from commercial sources. Furthermore, both magnetite and barium ferrite possess excellent magnetic properties.

[0090] In some embodiments, the preparation of ferric oxide is as follows: ferrous chloride tetrahydrate and ferric chloride hexahydrate are dissolved in hydrochloric acid, and ammonia is added. Nanoparticles are obtained through a co-precipitation reaction. After adding a hydrophobic reagent, the mixture is stirred for 1-5 hours to modify the nanoparticles for hydrophobicity. After washing, magnetic ferric oxide nanoparticles are obtained and dispersed in octane, toluene or cyclohexane for storage.

[0091] In some embodiments, the hydrophobic agent includes at least one of oleic acid, methacryloxypropyltrimethoxysilane, and dimethyloctadecyl[3-trihydroxysilylpropyl]ammonium chloride;

[0092] In some embodiments, the molar ratio of ferrous chloride tetrahydrate to ferric chloride hexahydrate is 1:1-5; this molar ratio can prepare iron(III) oxide with suitable particle size.

[0093] In some embodiments, the iron oxide is in the γ-crystalline form with a particle size of 8 nm-12 nm. This crystalline form and particle size of iron oxide exhibits good reactivity.

[0094] In some embodiments, the monomers used in the preparation of seed particles include styrene or methyl methacrylate; wherein styrene or methyl methacrylate, as monomers, have excellent reactivity.

[0095] In some embodiments, the mass ratio of magnetic nanoparticles to monomers is 1:2-6; this mass ratio enables the prepared magnetically responsive amphiphilic Janus nanoparticles to have a nanometer-scale particle size, and their morphology and size are suitable for direct use in droplet microfluidics.

[0096] In some embodiments, the crosslinking agent includes dicumyl peroxide or divinylbenzene; dicumyl peroxide or divinylbenzene has good crosslinking properties.

[0097] In some embodiments, the amount of crosslinking agent used is 0.5%-3% of the monomer mass; the amount of crosslinking agent used results in magnetically responsive amphiphilic Janus nanoparticles with a particle size in the nanometer range, and whose morphology and size are suitable for direct use in droplet microfluidics.

[0098] In some embodiments, the organic solvent includes at least one of octane, toluene, or cyclohexane; wherein octane, toluene, or cyclohexane, as organic solvents, have the advantages of good solubility and low cost.

[0099] In some embodiments, the polar solvent is an aqueous solution containing a nonionic surfactant, wherein the concentration of the nonionic surfactant in the aqueous solution is 1.2 g / L to 3.0 g / L, and the nonionic surfactant includes at least one of Tween 20, Span 80, or Triton X-405.

[0100] In some embodiments, the amount of polar solvent used is 50 to 100 times the mass of the monomer; this amount of polar solvent can provide a better reaction environment.

[0101] In some embodiments, the inert gas includes nitrogen or argon; wherein, nitrogen or argon, as an inert gas, has a better protective effect.

[0102] In some embodiments, the initiator comprises an aqueous solution of azobisisobutyronitrile or an aqueous solution of potassium persulfate; the initiator is capable of effectively promoting the polymerization reaction.

[0103] In some embodiments, the amount of initiator used is 1%-5% of the monomer mass; this amount of initiator is sufficient to promote the polymerization reaction well.

[0104] In some embodiments, the dispersion method includes one of ultrasonication, vortexing, or stirring; wherein ultrasonication, vortexing, or stirring are all easy-to-operate methods with relatively low operating costs.

[0105] In some embodiments, the resulting mixture is then dispersed in a polar solvent and stirred under an inert gas atmosphere for 0.5-1 hour. An initiator is then added, and stirring continues under an inert gas atmosphere for 1-3 hours. The mixture is heated to 60-80°C while stirring and reacted for 18-24 hours. The mixture is then centrifuged and washed three times alternately with water and anhydrous ethanol to obtain seed particles. The stirring speed is 300-900 rpm. The above polymerization reaction conditions are relatively mild, and the operating cost is low, making it suitable for large-scale production applications.

[0106] In some embodiments, during the preparation of the magnetically responsive Janus particles, the mass ratio of seed particles to the mixture is 1:500-700; the mass ratio of nonpolar solvent to alkaline solution in the mixture is 1:1.5-2.5; the nonpolar solvent includes at least one of ethanol or isopropanol.

[0107] In some embodiments, the alkaline solution includes at least one of ammonia, triethanolamine, or aminomethylpropanol.

[0108] In some embodiments, the hydrophilic polymer monomer includes at least one of lactic acid, acrylic acid, or ethyl orthosilicate; wherein, lactic acid, acrylic acid, or ethyl orthosilicate, as hydrophilic polymer monomers, not only have the advantage of good hydrophilicity, but also good reactivity and low production cost.

[0109] In some embodiments, the mass ratio of seed particles to hydrophilic polymer monomers is 1:13-56; this mass ratio of seed particles to hydrophilic polymer monomers results in magnetically responsive amphiphilic Janus nanoparticles with a nanometer-scale particle size and morphology and size suitable for direct use in droplet microfluidics.

[0110] In some embodiments, the stirring reaction time is 6-20 hours, and the stirring speed is 200-500 rpm. The stirring operation promotes the reaction and results in more uniform particle size of the prepared magnetically responsive amphiphilic Janus nanoparticles.

[0111] In some embodiments, the washing process involves alternating between water and anhydrous ethanol three times. This alternating washing with water and anhydrous ethanol three times ensures thorough cleaning.

[0112] A magnetically responsive amphiphilic Janus nanoparticle is prepared by the above-described method for preparing magnetically responsive amphiphilic Janus nanoparticles.

[0113] Among them, the magnetically responsive amphiphilic Janus nanoparticles have a particle size of 100nm-500nm, are uniform in size, and contain three components, thus possessing greater application value. Furthermore, these Janus nanoparticles can be directly used in droplet microfluidic generation to produce stable, uniformly sized, and magnetically responsive emulsion droplets.

[0114] A method for preparing a Pickering emulsion, the Pickering emulsion comprising magnetically responsive amphiphilic Janus nanoparticles obtained by the above-described method for preparing magnetically responsive amphiphilic Janus nanoparticles, comprising the following steps:

[0115] The magnetically responsive amphiphilic Janus nanoparticles are dispersed in an aqueous phase, and then an oil phase is added. The oil and water phases are emulsified by stirring to form a water-in-oil or oil-in-water Pickering emulsion, thus obtaining the Pickering emulsion.

[0116] The method for preparing this Pickering emulsion has the advantages of being mild and low-cost. Furthermore, the resulting Pickering emulsion exhibits tunable amphiphilicity and can be directly generated into stable, uniformly sized, and magnetically corresponding emulsion droplets using microfluidic technology.

[0117] In some embodiments, the dispersion method includes ultrasound; ultrasound can uniformly disperse magnetically responsive amphiphilic Janus nanoparticles in an aqueous phase and has relatively low operating costs.

[0118] In some embodiments, the oil phase includes at least one of hexadecane, mineral oil, or soybean oil; wherein the selected oil phase is suitable for forming emulsion droplets and is relatively inexpensive.

[0119] In some embodiments, the stirring method includes vortexing; wherein stirring by vortexing can make the oil and water phases emulsified uniformly and has a relatively low operating cost.

[0120] In some embodiments, the stirring speed is 200 rpm to 500 rpm, and the stirring time is 6 h to 20 h.

[0121] In some embodiments, the concentration of magnetically responsive amphiphilic Janus nanoparticles in the Pickering emulsion is 0.4 mg / mL to 2 mg / mL; this concentration of Pickering emulsion is suitable for use as a surfactant.

[0122] In some embodiments, the volume ratio of the aqueous phase to the oil phase is 1-9:1-9; this volume ratio makes the prepared surfactant suitable for direct use in droplet microfluidics.

[0123] In some embodiments, when the mass ratio of seed particles to hydrophilic polymer monomers is <1:38, a water-in-oil Pickering emulsion is formed using magnetically agitated amphiphilic Janus nanoparticles; when the mass ratio of seed particles to hydrophilic polymer monomers is >1:38, a water-in-oil Pickering emulsion is formed using magnetically agitated amphiphilic Janus nanoparticles. By adjusting the mass ratio of seed particles to hydrophilic polymer monomers, the synthesized particles can have different hydrophilicity / hydrophobicity, thus resulting in different hydrophilicity / hydrophobicity of the Pickering emulsion.

[0124] A Pickering emulsion is prepared by the above-described method for preparing a Pickering emulsion.

[0125] This Pickering emulsion has adjustable amphiphilicity and can directly generate stable, uniformly sized, and magnetically corresponding emulsion droplets using microfluidic technology.

[0126] The magnetically responsive amphiphilic Janus nanoparticles prepared by the method are used as solid surfactants.

[0127] Application of magnetically responsive amphiphilic Janus nanoparticles prepared by a specific method in droplet microfluidics.

[0128] In some embodiments, magnetically responsive amphiphilic Janus nanoparticles are used in microfluidic channels and dispersed in a dispersed phase as the inner phase, with a fluid of opposite polarity to the inner phase as the outer phase. The inner and outer phases are introduced into a flow-focusing PDMS microfluidic chip or a glass capillary device by a fluid injection pump or a pressure injection pump. By adjusting the flow rate and flow rate ratio of the two phases, the size of the generated droplets is controlled to obtain water-in-oil droplets or oil-in-water droplets.

[0129] In some embodiments, when forming oil-in-water droplets, the volumetric flow rate ratio of the inner phase to the outer phase is 1:20-280; when forming water-in-oil droplets, the volumetric flow rate ratio of the inner phase to the outer phase is 1:1-15.

[0130] Specifically, when the Pickering emulsion is formed by droplet microfluidics, the polydispersity of the resulting size is <5%. Furthermore, the Pickering emulsion exhibits a response range of 0.1T–0.7T to an applied magnetic field.

[0131] Among them, the magnetically responsive amphiphilic Janus nanoparticles can directly generate a large number of stable, uniformly sized, and magnetically responsive emulsion droplets through microfluidic technology.

[0132] In some embodiments, when the mass ratio of seed particles to hydrophilic polymer monomers is <1:38, the prepared magnetically responsive amphiphilic Janus nanoparticles are dispersed in an aqueous phase at a concentration of 0.04wt%-0.2wt% and serve as the internal phase. In addition, non-polar fluids such as hexadecane or soybean oil serve as the external phase and are introduced into the corresponding channels of the flow-focusing PDMS microfluidic chip to form an oil-in-water emulsion.

[0133] In some embodiments, when the mass ratio of seed particles to hydrophilic polymer monomers is >1:38, the prepared magnetically responsive amphiphilic Janus nanoparticles are dispersed in the oil phase at a concentration of 0.04wt%-0.2wt% and serve as the inner phase. In addition, water serves as the outer phase and is introduced into the corresponding flow channels of the self-made glass capillary device to form an oil-in-water emulsion.

[0134] The following provides a further explanation using specific implementation methods.

[0135] Example 1

[0136] The preparation of hydrophobic, magnetically responsive amphiphilic Janus nanoparticles includes the following steps:

[0137] (1) Weigh 2.5g FeCl2·4H2O and 0.9g FeCl3·6H2O, and dissolve them in 12.5mL of dilute hydrochloric acid to obtain a solution with a concentration of 1mol / L. Then, under magnetic stirring, add 10mL of concentrated ammonia water with a mass concentration of 25% to the solution. After stirring for 2h, add 0.5mL of oleic acid to the reaction system and continue stirring for 1h. Finally, centrifuge the obtained product and wash it three times alternately with deionized water and ethanol to obtain magnetic nanoparticles. Then, disperse the magnetic nanoparticles in octane to obtain a dispersion with a mass concentration of 20wt%.

[0138] (2) 1.5 g of the obtained magnetic nanoparticle dispersion, 1.08 g of styrene, and 0.02 g of azobisisobutyronitrile were added to 30 mL of deionized water (containing 2 g / L Triton x-405). The mixture was then sonicated for 2 h using a cell ultrasonic disruptor at 350 W power with a 2 s working and 1 s intermittent parameter to obtain an emulsion. The emulsion was then subjected to polymerization reaction at 400 rpm under magnetic stirring and 70 °C water bath heating for 2 h. The product generated by the polymerization reaction was centrifuged and washed three times alternately with deionized water and ethanol to obtain seed particles.

[0139] (3) In a beaker, add 30 mL of isopropanol, 16 mL of ammonia (2% by mass), and 100 mg of seed particles (dry weight). Then place the beaker in a cell ultrasonic disruptor and sonicate for 60 min at 350 W power, 2 s working time, and 1 s interval to obtain a dispersion. Then transfer the dispersion to a two-necked flask with a stirrer. While stirring, add 0.325 mL of ethyl orthosilicate dispersion in 17 mL of isopropanol using a syringe pump at a rate of 65 μL / min. After adding all the solution, keep stirring and react at room temperature for 12 h. Then centrifuge to separate the product and wash the product three times with deionized water and ethanol alternately to obtain hydrophobic magnetically responsive amphiphilic Janus nanoparticles.

[0140] The scanning electron microscope image of the magnetically responsive amphiphilic Janus nanoparticles prepared in this embodiment is shown below. Figure 1 As shown, the particle size range of the magnetically responsive amphiphilic Janus nanoparticles is 100nm-300nm.

[0141] The infrared absorption spectra of the magnetic nanoparticles, seed particles, and magnetically responsive amphiphilic Janus nanoparticles obtained in this embodiment are shown below. Figure 2 As shown in the figure, Fe3O4 NPs represent magnetic nanoparticles, Fe3O4@PS NPs represent seed particles, and Fe3O4@PS-SiO2 NPs represent magnetically responsive amphiphilic Janus nanoparticles. The infrared spectrum of Fe3O4 NPs shows that at 600 cm⁻¹... -1 A distinct Fe-O bond characteristic peak was observed at 3000 cm⁻¹; the infrared spectrum of Fe₃O₄@PS NPs, while retaining the Fe-O bond characteristic peak, also showed a distinct Fe-O bond characteristic peak at 3000 cm⁻¹. -1 1500cm -1 A distinct styrene characteristic peak was observed at 1100 cm⁻¹; the infrared spectrum of Fe₃O₄@PS-SiO₂ NPs, while retaining the characteristic peaks of Fe-O bonds and polystyrene, also showed a distinct styrene characteristic peak at 1100 cm⁻¹. -1 A distinct Si-O-Si bond characteristic peak was observed at the location.

[0142] The hysteresis loop and response diagram under a magnetic field of the magnetically responsive amphiphilic Janus nanoparticles prepared in this embodiment are shown below. Figure 3 As shown, the hysteresis loop test plot indicates that the magnetically responsive amphiphilic Janus nanoparticles possess superparamagnetism.

[0143] Among them, the prepared hydrophilic magnetically responsive amphiphilic Janus nanoparticles can be used as solid surfactants.

[0144] Example 2

[0145] The preparation of hydrophilic, magnetically responsive amphiphilic Janus nanoparticles includes the following steps:

[0146] (1) Weigh 2.5g FeCl2·4H2O and 0.9g FeCl3·6H2O, and dissolve them in 12.5mL of dilute hydrochloric acid to obtain a solution with a concentration of 1mol / L. Then, under magnetic stirring, add 10mL of concentrated ammonia water with a mass concentration of 25% to the solution. After stirring for 2h, add 0.5mL of oleic acid to the reaction system and continue stirring for 1h to obtain the product. Then, centrifuge the obtained product and wash it three times alternately with deionized water and ethanol to obtain magnetic nanoparticles. Then, disperse the magnetic nanoparticles in octane to obtain a dispersion with a mass concentration of 20wt%.

[0147] (2) 1.5 g of the obtained magnetic nanoparticle dispersion, 1.08 g of styrene, and 0.02 g of azobisisobutyronitrile were added to 30 mL of deionized water (containing 2 g / L Triton x-405). The mixture was then sonicated for 2 h using a cell ultrasonic disruptor at 350 W power with a 2 s working and 1 s intermittent parameter to obtain an emulsion. The emulsion was then subjected to polymerization reaction at 400 rpm under magnetic stirring and 70 °C water bath heating for 2 h to obtain the product. The product was then centrifuged and washed three times alternately with deionized water and ethanol to obtain seed particles.

[0148] (3) In a beaker, add 30 mL of isopropanol, 16 mL of ammonia (2% by mass), and 100 mg of seed particles (dry weight). Then place the beaker in a cell ultrasonic disruptor and sonicate for 60 min at 350 W power, 2 s working time, and 1 s intermittent time to obtain a dispersion. Then transfer the dispersion to a two-necked flask with a stirrer. While stirring, add 0.525 mL of ethyl orthosilicate dispersion in 17 mL of isopropanol using a syringe pump at a rate of 65 μL / min. After adding all the solution, keep stirring and react at room temperature for 12 h. Centrifuge to separate the product and wash it three times with deionized water and ethanol alternately to obtain hydrophilic magnetically responsive amphiphilic Janus nanoparticles.

[0149] Among them, the prepared hydrophilic magnetically responsive amphiphilic Janus nanoparticles can be used as solid surfactants.

[0150] Example 3

[0151] A method for preparing a Pickering emulsion includes the following steps:

[0152] The magnetically responsive amphiphilic Janus nanoparticles prepared in Example 1 were added at a concentration of 0.2 wt% to glass vials containing different oil-to-water ratios to prepare samples. The oil-to-water ratio refers to the mass ratio of hexadecane to deionized water. Four samples with different oil-to-water ratios were prepared: 1:9, 3:7, 5:5, and 7:3. Each of the four samples was then vortexed for 1 min to form a water-in-oil emulsion (see [link to example]). Figure 4 ), which is a surfactant. Figure 4 Among them, the oil-to-water emulsion labeled 'a' has an oil-to-water ratio of 1:9, 'b' has an oil-to-water ratio of 3:7, 'c' has an oil-to-water ratio of 5:5, and 'd' has an oil-to-water ratio of 7:3. These oil-to-water emulsions exhibit good long-term storage stability and can be stably stored for more than one month without external influences.

[0153] in, Figure 5 This is a fluorescence image of a water-in-oil emulsion with an oil-to-water ratio of 1:9. In the image, the spherical particles represent the aqueous phase.

[0154] Example 4

[0155] A method for preparing a Pickering emulsion includes the following steps:

[0156] The magnetically responsive amphiphilic Janus nanoparticles prepared in Example 2 were added at a concentration of 0.2 wt% to glass vials containing different oil-to-water ratios to prepare samples. The oil-to-water ratio refers to the mass ratio of hexadecane to deionized water. Four samples with different oil-to-water ratios were prepared: 1:9, 3:7, 5:5, and 7:3. Each of the four samples was then vortexed for 1 min to form an oil-in-water emulsion (see [link to example]). Figure 6 ), which is a surfactant. Figure 6 Among them, the oil-in-water emulsion labeled 'a' has an oil-to-water ratio of 1:9, 'b' has an oil-to-water ratio of 3:7, 'c' has an oil-to-water ratio of 5:5, and 'd' has an oil-to-water ratio of 7:3. These oil-in-water emulsions exhibit good long-term storage stability and can be stably stored for more than one month without external influences.

[0157] in, Figure 7 This is a fluorescence image of an oil-in-water emulsion with an oil-to-water ratio of 1:9. In the image, the spherical particles represent the oil phase.

[0158] Example 5

[0159] Application of magnetically responsive amphiphilic Janus nanoparticles in droplet microfluidics:

[0160] Formation of a uniform water-in-oil emulsion: The magnetically responsive amphiphilic Janus nanoparticles prepared in Example 1 were dispersed in deionized water at a particle concentration of 0.2 wt% as the inner phase and hexadecane as the outer phase. The inner and outer phases were introduced into a two-phase flow focusing PDMS microfluidic chip with a shear orifice size of 125 μm using a fluid injection pump. The flow rates of the inner and outer phases were set to 1 μL / min and 10 μL / min, respectively, and a water-in-oil emulsion with a size of 30 μm was finally obtained.

[0161] Among them, the physical image and optical microscope image of the water-in-oil emulsion obtained by applying the liquid magnetically responsive amphiphilic Janus nanoparticles in droplet microfluidics are shown, as follows: Figure 8 As shown in the figure. The top image is a photograph of the water-in-oil emulsion, and the bottom image is an optical microscope image of the droplets. It can be seen that, using microfluidics, these hydromagnetically responsive amphiphilic Janus nanoparticles can form uniformly sized water-in-oil droplets, such as... Figure 8 In the optical microscope image of the droplet, it can be clearly seen that the size uniformity of the water-in-oil droplet is very good.

[0162] Example 6

[0163] Application of magnetically responsive amphiphilic Janus nanoparticles in droplet microfluidics:

[0164] Generation of a uniform oil-in-water emulsion: The magnetically responsive amphiphilic Janus nanoparticles prepared in Example 2 were dispersed in hexadecane at a particle concentration of 0.2 wt% as the inner phase and deionized water as the outer phase. The inner and outer phases were introduced into a two-phase glass capillary device with a shear orifice size of 200 μm using a fluid injection pump. The flow rates of the inner and outer phases were set to 1 μL / min and 80 μL / min, respectively, and an oil-in-water emulsion with a size of 25 μm was finally obtained.

[0165] Among them, the physical image and optical microscope image of the oil-in-water emulsion obtained by applying the magnetically responsive amphiphilic Janus nanoparticles in droplet microfluidics are shown, for example. Figure 9 As shown in the figure, the top image is a physical image of the oil-in-water emulsion, and the bottom image is an optical microscope image of the droplet. It can be seen that, using microfluidics, these hydromagnetically responsive amphiphilic Janus nanoparticles can form uniformly sized oil-in-water droplets. The excellent size uniformity of these droplets is clearly visible under an optical microscope.

[0166] Experimental Test

[0167] Test of magnetic field response

[0168] The emulsions obtained in Example 5 or Example 6 were placed in a quartz jar containing an external phase solution. A magnet with a maximum magnetic field strength of 0.3T was moved at a distance of 1 cm from the emulsion droplet. It was observed that the droplet moved with the movement of the magnet. Therefore, the oil-in-water emulsion or water-in-oil emulsion formed by the magnetically responsive amphiphilic Janus nanoparticles of the present invention in droplet microfluidics have good magnetic field responsiveness.

[0169] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A method for preparing magnetically responsive amphiphilic Janus nanoparticles, characterized in that, Includes the following steps: Preparation of seed particles: Magnetic nanoparticles, monomers and crosslinking agents are dispersed in an organic solvent, and then the resulting mixture is added to a polar solvent. After stirring under an inert gas atmosphere, an initiator is added, and stirring is continued under an inert gas atmosphere. The reaction is carried out while stirring and heating. Then, the mixture is centrifuged and washed to obtain seed particles. Preparation of magnetically responsive Janus particles: The seed particles were dispersed in a mixture containing a polar solvent and an alkaline solution, then ethyl orthosilicate was added, and the mixture was stirred and reacted at room temperature. After centrifugation and washing, magnetically responsive Janus particles were obtained.

2. The method for preparing magnetically responsive amphiphilic Janus nanoparticles according to claim 1, characterized in that, In the preparation of the seed particles, the magnetic nanoparticles comprise iron(II,III) oxide and / or barium ferrite; and / or Preparation of the Fe3O4: Ferrous chloride tetrahydrate and ferric chloride hexahydrate are dissolved in hydrochloric acid, and ammonia is added. Nanoparticles are obtained through co-precipitation reaction. After adding a hydrophobic reagent, the mixture is stirred for 1-5 hours to modify the nanoparticles for hydrophobicity. After washing, magnetic Fe3O4 nanoparticles are obtained and stored in octane, toluene or cyclohexane. The hydrophobic agent includes at least one of oleic acid, methacryloyloxypropyltrimethoxysilane, and dimethyloctadecyl[3-trihydroxysilylpropyl]ammonium chloride; The molar ratio of ferrous chloride tetrahydrate to ferric chloride hexahydrate is 1:1-5; The iron(III) oxide is in the γ-crystalline form with a particle size of 8 nm-12 nm.

3. The method for preparing magnetically responsive amphiphilic Janus nanoparticles according to claim 1, characterized in that, In the preparation of the seed particles, the monomer includes styrene or methyl methacrylate; and / or The mass ratio of the magnetic nanoparticles to the monomer is 1:2-6; and / or The crosslinking agent is divinylbenzene; and / or The amount of the crosslinking agent is 0.5%-3% of the monomer mass; and / or The organic solvent includes at least one of octane, toluene, or cyclohexane; and / or The polar solvent is an aqueous solution containing a nonionic surfactant, wherein the concentration of the nonionic surfactant in the aqueous solution is 1.2 g / L-3.0 g / L, and the nonionic surfactant includes at least one of Tween 20, Span 80, or Triton X-405; and / or The amount of the polar solvent used is 50 to 100 times the mass of the monomer; and / or The inert gas includes nitrogen or argon; and / or The initiator includes an aqueous solution of azobisisobutyronitrile or an aqueous solution of potassium persulfate; and / or The amount of the initiator is 1%-5% of the monomer mass; and / or The dispersion method includes one of ultrasonication, vortexing, or stirring; and / or The resulting mixture was then dispersed in a polar solvent and stirred under an inert gas atmosphere for 0.5 h–1 h. An initiator was then added, and stirring continued under an inert gas atmosphere for 1 h–3 h. The mixture was heated to 60 ℃–80 ℃ while stirring and reacted for 18 h–24 h. The mixture was then centrifuged and washed three times alternately with water and anhydrous ethanol to obtain seed particles. The stirring speed was 300 rpm–900 rpm.

4. The method for preparing magnetically responsive amphiphilic Janus nanoparticles according to claim 1, characterized in that, In the preparation of the magnetically responsive Janus particles, the mass ratio of the seed particles to the mixture is 1:500-700; In the mixture, the mass ratio of polar solvent to alkaline solution is 1:1.5-2.5; The polar solvent includes at least one of ethanol or isopropanol; The alkaline solution includes at least one of ammonia, triethanolamine, or aminomethylpropanol; The mass ratio of the seed particles to ethyl orthosilicate is 1:13-56; The stirring reaction time is 6 h-20 h, and the stirring speed is 200 rpm-500 rpm; The washing process involves alternating between washing with water and anhydrous ethanol three times.

5. A magnetically responsive amphiphilic Janus nanoparticle, characterized in that, It is prepared by the method for preparing magnetically responsive amphiphilic Janus nanoparticles as described in any one of claims 1 to 4.

6. A method for preparing a Pickering emulsion, characterized in that, The Pickering emulsion comprises magnetically responsive amphiphilic Janus nanoparticles prepared by the method for preparing magnetically responsive amphiphilic Janus nanoparticles according to any one of claims 1 to 4, comprising the following steps: The magnetically responsive amphiphilic Janus nanoparticles are dispersed in an aqueous phase, and then an oil phase is added. The oil and water phases are emulsified by stirring to form a water-in-oil or oil-in-water Pickering emulsion, thus obtaining the Pickering emulsion.

7. The method for preparing a Pickering emulsion according to claim 6, characterized in that, The dispersion methods include ultrasonication, stirring, and vortexing; The oil phase includes at least one of hexadecane, mineral oil, or soybean oil; In the Pickering emulsion, the concentration of the magnetically responsive amphiphilic Janus nanoparticles is 0.4 mg / mL to 2 mg / mL; The volume ratio of the aqueous phase to the oil phase is 1-9:1-9. When the mass ratio of the seed particles to orthoethyl silicate is <1:38, the Pickering emulsion formed using the magnetically agitated amphiphilic Janus nanoparticles is an oil-in-water emulsion; when the mass ratio of the seed particles to orthoethyl silicate is >1:38, the Pickering emulsion formed using the magnetically agitated amphiphilic Janus nanoparticles is a water-in-oil emulsion.

8. The magnetically responsive amphiphilic Janus nanoparticles prepared by the method according to any one of claims 1 to 4 are used as solid surfactants.

9. The application of magnetically responsive amphiphilic Janus nanoparticles prepared by the method according to any one of claims 1 to 4 in droplet microfluidics.

10. The application of the magnetically responsive amphiphilic Janus nanoparticles according to claim 9 in droplet microfluidics, characterized in that, The magnetically responsive amphiphilic Janus nanoparticles are dispersed in a dispersed phase as the inner phase, and a fluid with the opposite polarity to the inner phase is used as the outer phase. The inner and outer phases are introduced into a flow-focusing PDMS microfluidic chip or a glass capillary device by a fluid injection pump or a pressure injection pump. By adjusting the flow rate and flow rate ratio of the two fluids, the size of the generated droplets is controlled to obtain water-in-oil droplets or oil-in-water droplets. When forming oil-in-water droplets, the volumetric flow rate ratio of the internal phase to the external phase is 1:20-280; when forming water-in-oil droplets, the volumetric flow rate ratio of the internal phase to the external phase is 1:1-15.

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